What triggers the secretion of glucagon from the pancreas?

Glucagon secretion from the pancreas is primarily triggered by low blood glucose levels. When blood glucose levels drop, the alpha cells of the islets of Langerhans in the pancreas release glucagon into the bloodstream. This hormone plays a critical role in maintaining blood glucose homeostasis.

Glucagon acts on the liver to promote the conversion of glycogen to glucose (glycogenolysis) and facilitates gluconeogenesis, the process of creating glucose from non-carbohydrate sources. As a result, glucagon effectively raises blood glucose levels, counteracting hypoglycemia to ensure a steady supply of glucose for energy, particularly for the brain and muscles.

In contrast, high blood glucose levels would trigger the secretion of insulin, which serves to lower blood glucose levels. High calcium and low oxygen levels do not have direct significant impacts on glucagon secretion. Thus, the body has specific mechanisms to respond to varying blood glucose levels, with glucagon being essential for responding to hypoglycemia.